Experts say incidents of violent driving, known as road rage, have been on the rise in the United States for the past several years. There is even a name for the condition that supposedly triggers the outbursts. Even the most mild-mannered person can be transformed into a dangerous driver.

The American Automobile Association says incidents of road rage have increased seven percent in the United States in recent years. Road rage can be anything from a hostile glare to threats of violence. Experts say stress due to bad driving, long commutes, congested roads and busy lifestyles is contributing to the frustration.

Stosny says those are just the minor aches and pains. “You are three-and-a-half times more likely to develop heart disease, nine times more likely to develop high blood pressure," he said.

Nikki Cooper says her road rage was a symptom of something worse. She was diagnosed with a condition known as Intermittent Explosive Disorder, or I.E.D., an imbalance of brain chemicals, which causes people to blow up into anger unexpectedly. Medical experts say the disorder affects up to one in 20 people. Men are more commonly affected than women.

Doctors say the most minor traffic trouble can drive I.E.D. sufferers into a rage that is difficult to control. Dr. Emil Coccaro of the University of Chicago said, "They're having low-level outbursts, screaming, shouting, slamming doors, or they're having at least three episodes a year where they're destroying large amounts of property or hurting people."

Researchers say I.E.D. typically begins at home with abuse toward a spouse and children, but something like a traffic jam can aggravate the problem, as Mary McFee discovered. "It just feels like an explosion of rage, and I try to stop it and it doesn't stop,” she said.

Stosny says people with I.E.D. should try to use other modes of transportation. "If you have I.E.D. you probably shouldn't drive because you're more likely to get it triggered because of the stress of driving," he said.

I.E.D. can be controlled with medication and therapy, which Cooper finds helpful, both while driving and at home. Cooper said, "You're really putting yourself in dangerous situations for really little things."

Whether road rage is associated with I.E.D. or just an angry driver, automotive groups say people need to control themselves because they are hurting themselves and potentially others on the road.